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The case of white nationalist Thomas Mair is a sign of things to come.

The U.K.’s Central Criminal Court just sentenced Mair, 53, to a life term for the murder of Labour MP Jo Cox. According to the Guardian, Cox’s opposition to Brexit and her desire to bring Syrian child refugees to Britain enraged Mair:

Thomas Mair repeatedly shot and stabbed Cox in an attack during the EU referendum campaign in June. While attacking her he was saying “this is for Britain”, “keep Britain independent”, and “Britain first”, the court heard.

“Britain First” is the name of an Islamophobic, white nationalist organization and political party. Police investigation later discovered that Mair had long been connected to white nationalist movements, including pro-apartheid and neo-Nazi groups. “There is no doubt that this murder was done to advance the cause of violent white nationalism,” Mr. Justice Wilkie asserted during sentencing today.

Mair will now live out the rest of his days in prison. But the ideology he serviced will not be so easily contained. The election of Donald Trump has provided white nationalists fresh momentum; though they have not attacked an elected official for opposing him, America’s own history of racist violence suggests it’s far from impossible. The murder of Jo Cox is a tragedy and a warning.